Today we set the sender to the FROM of the message. So you should see it both in the listing and also in the message view. We can explore adding this to the title/subject if there is enough interest. Please file it as an RFE in http://bugzilla.zimbra.com and make a vote. If enough people vote on it we'll make the change.

Looking for new beta users -> Co-Founder of Acompli. Previously worked at Zimbra (and Yahoo! & VMware) since 2005.